The European Commission has raised the prospect of Apple being forced to open the closed link between iTunes, its dominant online music store, and its iPod music players.

Meglena Kuneva, the Consumer Protection Commissioner, said that "something has to change" in Apple's present system, under which tracks bought on iTunes work only on iPods.

She told the German magazine Focus: "Do you think it's fine that a CD plays in all CD players but that an iTunes song only plays in an iPod? I don't."

Dr Kuneva is leading a review of Europe's cross-border consumer rights laws.

Her comments add to mounting pressure on Apple over iTunes, which accounts for as much as 80 per cent of the digital music market in some territories.

The Norwegian consumer ombudsman ruled in January that iTune's lack of interoperability with other devices was illegal, giving Apple until March 1 to respond and until October 1 to take action.

Soon afterwards, official consumer bodies in Germany, the Netherlands, Finland and France agreed a common stance, which demands that Apple give other manufacturers, such as Sony, Creative and Microsoft, access to iTunes.

Dr Kuneva's comments appear to signal a hardening of the Commission's line on Apple.

So far Brussels has said that it would need to study development in the relatively young market for music downloads.

Any proposals for change would be resisted fiercely by Apple.

Analysts widely believe that the company uses iTunes to lock consumers into its own music technology and have pointed out that iPod sales were modest until the launch of iTunes in 2004.

When French lawmakers raised the prospect of Apple being forced to open up iTunes, Apple insiders suggested that the company would rather quit France.

EMI and Sony BMG, the music labels, have experimented with selling downloads free from digital rights management (DRM) technology, which limits where a track can be played, ostensibly to guard against piracy.

Steve Jobs, the Apple chief executive, insisted recently that Apple would drop its DRM system "in a heartbeat", but added that his hands were effectively tied by the record companies.

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